The document summarizes key concepts about Strings in Java including: 1. Strings can be created using double quotes or by converting a character array to a String. 2. The length() method returns the number of characters in a String. 3. Strings can be concatenated using the + operator or concat() method. 4. The format() method can be used to create formatted String outputs. 5. Common String methods include charAt(), compareTo(), indexOf(), and length().

1. Computer
Programming 2
Lesson 12– Java – Strings Class
Prepared by: Analyn G. Regaton

2. Creating
Strings
The most direct way to create a string is to write −
String greeting = "Hello world!";Example
public class StringDemo {
public static void main(String args[]) {
char[] helloArray = { 'h', 'e', 'l', 'l', 'o', '.' };
String helloString = new String(helloArray);
System.out.println( helloString );
}
}
Output
hello.
Note − The String class is immutable, so that once it is created a
String object cannot be changed. If there is a necessity to make a
lot of modifications to Strings of characters, then you should
use String Buffer & String Builder Classes.

3. String Length
public class StringDemo {
public static void main(String args[]) {
String palindrome = "Dot saw I was Tod";
int len = palindrome.length();
System.out.println( "String Length is : " + len );
}
}
Output
String Length is : 17
Methods used to obtain information about an object are known
as accessor methods. One accessor method that you can use
with strings is the length() method, which returns the number
of characters contained in the string object.

4. Concatenating
Strings
The String class includes a method for concatenating
two strings −
string1.concat(string2);
This returns a new string that is string1 with string2
added to it at the end. You can also use the concat()
method with string literals, as in −
"My name is ".concat("Zara");
Strings are more commonly concatenated with the +
operator, as in −
"Hello," + " world" + "!"
which results in −
"Hello, world!"

5. EXA0*3E
*R0GRA0
public class StringDemo {
public static void main(String args[]) {
String string1 = "saw I was ";
System.out.println("Dot " + string1 + "Tod");
}
}
Output
Dot saw I was Tod

6. Creating
Format Strings
You have printf() and format() methods to
print output with formatted numbers.
The String class has an equivalent class
method, format(), that returns a String
object rather than a PrintStream object.
Using String's static format() method
allows you to create a formatted string
that you can reuse, as opposed to a one-
time print statement.

7. EXA0*3E
*R6GRA0
System.out.printf("The value of the float variable is " +
"%f, while the value of the integer " +
"variable is %d, and the string " +
"is %s", floatVar, intVar, stringVar);
You can write −
String fs;fs = String.format("The value of the float variable is " +
"%f, while the value of the integer " +
"variable is %d, and the string " +
"is %s", floatVar, intVar,
stringVar);System.out.println(fs);

8. String
Methods
Sr.No. Method & Description
1 char charAt(int index)
Returns the character at the specified index.
2 int compareTo(Object o)
Compares this String to another Object.
3 int compareTo(String anotherString)
Compares two strings lexicographically.
4 int compareToIgnoreCase(String str)
Compares two strings lexicographically, ignoring case differences.
5 String concat(String str)
Concatenates the specified string to the end of this string.
6 boolean contentEquals(StringBuffer sb)
Returns true if and only if this String represents the same sequence of
characters as the specified StringBuffer.

9. String
Methods
Sr.No. Method & Description
7 static String copyValueOf(char[] data)
Returns a String that represents the character sequence in the array
specified.
8 static String copyValueOf(char[] data, int offset, int count)
Returns a String that represents the character sequence in the array
specified.
9 boolean endsWith(String suffix)
Tests if this string ends with the specified suffix.
10 boolean equals(Object anObject)
Compares this string to the specified object.
11 boolean equalsIgnoreCase(String anotherString)
Compares this String to another String, ignoring case considerations.
12 byte[] getBytes()
Encodes this String into a sequence of bytes using the platform's default
charset, storing the result into a new byte array.

10. String
Methods
Sr.No. Method & Description
13 byte[] getBytes(String charsetName)
Encodes this String into a sequence of bytes using the named
charset, storing the result into a new byte array.
14 void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
Copies characters from this string into the destination character
array.
15 int hashCode()
Returns a hash code for this string.
16 int indexOf(int ch)
Returns the index within this string of the first occurrence of the
specified character.
17 int indexOf(int ch, int fromIndex)
Returns the index within this string of the first occurrence of the
specified character, starting the search at the specified index.

11. String
Methods
Sr.No. Method & Description
18 int indexOf(String str)
Returns the index within this string of the first occurrence of the
specified substring.
19 int indexOf(String str, int fromIndex)
Returns the index within this string of the first occurrence of the
specified substring, starting at the specified index.
20 String intern()
Returns a canonical representation for the string object.
21 int lastIndexOf(int ch)
Returns the index within this string of the last occurrence of the
specified character.
22 int lastIndexOf(int ch, int fromIndex)
Returns the index within this string of the last occurrence of the
specified character, searching backward starting at the specified
index.

12. String
Methods
Sr.No. Method & Description
23 int lastIndexOf(String str)
Returns the index within this string of the rightmost occurrence of the
specified substring.
24 int lastIndexOf(String str, int fromIndex)
Returns the index within this string of the last occurrence of the specified
substring, searching backward starting at the specified index.
25 int length()
Returns the length of this string.
26 boolean matches(String regex)
Tells whether or not this string matches the given regular expression.
27 boolean regionMatches(boolean ignoreCase, int toffset, String other, int
ooffset, int len)
Tests if two string regions are equal.
28 boolean regionMatches(int toffset, String other, int ooffset, int len)
Tests if two string regions are equal.